Swift - Flipping view controllers disables IBOutlets

My app starts and I'm presenting VC1 on the top of tabBarController

tabBarController?.present(VC1, animated: false, completion: nil)

It presents first page and I have another page VC2. I make flip transition between these 2 pages by posting notification to the current opened VC0 in the tabBarController(not the presented one, but the one who is in index 0 in the tabBarController).The notifications triggers:

    if var topController = UIApplication.shared.keyWindow?.rootViewController {
        while let presentedViewController = topController.presentedViewController {
            topController = presentedViewController
        }
        let VC2 = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(identifier: "VC2") as! VC2
        UIView.transition(from: topController.view, to: VC2.view, duration: 0.85, options: [.transitionFlipFromLeft])
    }

This makes the flip, but it looks like the IBOutlets are not connected and the click is not detected.

You haven't keep any reference if VC2. So IBOutlet's action do not perform. You can try this example. It may be helpful for you.

ViewController.swift

import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
    }
    @IBAction func gotoNextPage(_ sender: Any) {
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let vc = storyboard.instantiateViewController(withIdentifier: "SecondViewController")
        GlobalVariable.transitionViewFrom(from: self, to: vc, subtype: nil, options: [.transitionFlipFromLeft])
    }
}

class GlobalVariable: NSObject {
    private static var sharedManager: GlobalVariable!
    public var allViewInstantController: [UIViewController]=[UIViewController]()
    public static let NUMBER_OF_VIEWCONTROLLER_OPEN_AT_A_TIME:Int = 5

    static func shared() -> GlobalVariable {
        if(sharedManager==nil){
            sharedManager=GlobalVariable()
        }
        return sharedManager
    }
    override private init() {
    }

    static func transitionViewFrom(from:UIViewController, to:UIViewController, subtype:CATransitionSubtype? = nil, options: UIView.AnimationOptions? = nil) -> Void {
        let timeDelay:Double=0.5
        GlobalVariable.checkPreviousView(_view:to)
        GlobalVariable.splashViewFrom(from: from, to:to, isAdd:true, subtype:subtype, options: options, timeDelay: timeDelay)
    }

    static func checkPreviousView(_view:UIViewController) -> Void {
        GlobalVariable.shared().allViewInstantController.append(_view)
        if(GlobalVariable.shared().allViewInstantController.count>GlobalVariable.NUMBER_OF_VIEWCONTROLLER_OPEN_AT_A_TIME){
            let myViewController = GlobalVariable.shared().allViewInstantController.first
            myViewController?.view.removeFromSuperview()
            GlobalVariable.shared().allViewInstantController.removeFirst()
        }
    }

    static func splashViewFrom(from:UIViewController, to:UIViewController, isAdd:Bool, subtype:CATransitionSubtype? = nil, options: UIView.AnimationOptions? = nil, timeDelay:Double) -> Void {
        do {
            if let subtype = subtype {
                let transition = CATransition()
                transition.duration = 0.25
                transition.isRemovedOnCompletion = true;
                transition.timingFunction = CAMediaTimingFunction(name:CAMediaTimingFunctionName.easeInEaseOut)
                transition.type = CATransitionType.push
                transition.subtype  = subtype
                from.view.layer.add(transition, forKey: kCATransition)
            }else if let options = options {
                UIView.transition(from: from.view, to: to.view, duration: timeDelay, options: options)
            }

            if(!isAdd){
                from.view.removeFromSuperview()
                if(GlobalVariable.shared().allViewInstantController.count>0){
                    GlobalVariable.shared().allViewInstantController.removeLast()
                }
            }else{
                if subtype != nil {
                    from.view.addSubview(to.view)
                }
            }
        }
    }

    static func dismissViewFrom(viewController:UIViewController, subtype:CATransitionSubtype) -> Void {
        let timeDelay=0.5
        GlobalVariable.splashViewFrom(from: viewController, to: UIViewController(), isAdd:false, subtype:subtype, timeDelay: timeDelay)
    }
}

SecondViewController.swift

import UIKit

class SecondViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

    }
    @IBAction func previousPage(_ sender: Any) {
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let vc = storyboard.instantiateViewController(withIdentifier: "ViewController")
        GlobalVariable.transitionViewFrom(from: self, to: vc, subtype: nil, options: [.transitionFlipFromLeft])
    }
}

For flip just change type. And change accordingly for back page transaction.

transition.type = CATransitionType(rawValue: "flip")

Another solution, you can try this.

ViewController.swift

import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        GlobalVariable.shared().rootViewController=self
    }
    @IBAction func gotoNextPage(_ sender: Any) {
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let vc = storyboard.instantiateViewController(withIdentifier: "SecondViewController")
        UIView.transition(from: self.view, to: vc.view, duration: 0.5, options: [.transitionFlipFromLeft])
    }
}

class GlobalVariable: NSObject {
    private static var sharedManager: GlobalVariable!
    public var rootViewController: UIViewController?
    static func shared() -> GlobalVariable {
        if(sharedManager==nil){
            sharedManager=GlobalVariable()
        }
        return sharedManager
    }
    override private init() {
    }
}

SecondViewController.swift

import UIKit

class SecondViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        GlobalVariable.shared().rootViewController=self
    }

    @IBAction func previousPage(_ sender: Any) {
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let vc = storyboard.instantiateViewController(withIdentifier: "ViewController")
        UIView.transition(from: self.view, to: vc.view, duration: 0.5, options: [.transitionFlipFromLeft])
    }
}